Effects of noise on telephone calls to the Madrid Regional Medical Emergency Service (SUMMA 112)

Highlights

• Nocturnal noise exceeded the WHO threshold (55 db(A)) on 100% of nights.

• For all causes, it was Leqn rather than Leqd that had a short-term effect on SUMMA 112 calls.

• SUMMA 112 data give access to real-time information on effects associated with noise levels.

• This impact being greater for respiratory than for circulatory causes.

Abstract

Background

Although the effects of noise on population morbidity and mortality have been observed both in the short and long term, the morbidity and mortality indicators used to date have not enabled information on such health effects to be accessed in real time. At an international level, there are relatively few studies, mostly recent, which have considered an alternative indicator, such as the demand for medical attention provided by emergency services, taking into account environmental factors other than noise.

Objectives

To ascertain the short-term effect of road-traffic noise levels on medical care, broken down by organic, circulatory and respiratory causes, provided by the Madrid Regional Medical Emergency Service (Servicio de Urgencia Médica de Madrid/SUMMA 112).

Methods

We used an ecological time-series study and fitted Poisson regression models, to analyse the number of daily, cause-specific episodes of care provided in situ by SUMMA 112, via emergency ambulance dispatches, across the period 01/01/2008–31/12/2009. To this end, we considered diurnal (Leqd: 7–23 h), nocturnal (Leqn: 23–7 h) and daily (Leq24: 24 h) noise (in db(A)) as the principal factor, and chemical air pollution (µg/m³) and temperature (°C) as the control variables. We also controlled for trend and seasonalities, the autoregressive nature of the series, and day of the week.

Results

Nocturnal noise exceeded the WHO threshold (55 db(A)) on 100% of nights, despite displaying a downward trend across the study period. For all causes, with the exception of emergency calls due to ischaemic disease, it was nocturnal rather than diurnal noise levels that had a short-term effect (lags 0–1) on SUMMA 112 calls, with this impact being greater for respiratory than for circulatory causes. Hence, for every increase of 1db in Leqn, the relative risks (RRs) were as follows: 1.11 (95% CI 1.09–1.13) for organic causes; 1.14 (95% CI: 1.11–1.18) for respiratory causes; and 1.08 (95% CI: 1.05–1.10) for circulatory causes.

Conclusion

SUMMA 112 data give access to real-time information on the health effects associated with increases in noise levels, which cannot be obtained via mortality or hospital-admission data, since these are collected in the longer term. Accordingly, this is something that would be immediately applicable in any future implementation of a syndromic surveillance system focusing on the effects of environmental pollutants on health.

Introduction

In Europe, approximately 20% of the population is exposed to diurnal road-traffic noise levels (Leqd) above the health protection threshold of 65 db(A) set by the WHO, while over 30% is exposed to levels above the nocturnal noise (Leqn) threshold of 55 db(A) (WHO, 2016). In Madrid (Spain), these thresholds were exceeded on 52% of days in the period 2003–2005 (Tobias et al., 2015a) and 100% of nights in the period 2003–2007 (Recio et al., 2016b) respectively.

Exposure to unacceptable noise levels as defined by the above criteria is considered a risk factor for human health. The physiological mechanism generated on receiving this external stimulus entails different stages, and is triggered as a response to a stressful situation. It has been observed that persons exposed to traffic noise show an increase in the levels of biological parameters, including adrenalin, cortisol, glucose, triglycerides and cholesterol, among others (Díaz and Linares, 2015). These levels, maintained over time, can have an influence on the development, progress and/or worsening of health conditions, such as cardiovascular diseases (including atherosclerosis, stroke, ischaemic heart disease and hypertension, among others), respiratory diseases, and diabetes. By reference to two levels of processing stress, i.e., psychological and physiological, the integrative model proposed by Recio (Recio et al., 2016a) shows how excitation of the hypothalamus due to perceived noise can involve a balanced physiological response without adverse effects if the emotional response is flexible, or alternatively, an allostatic overload with cardiovascular, respiratory and metabolic effects if the emotional response is rigid.

Noise has been observed to have effects on population morbidity and mortality in the short and long term, even in the childhood population. In the short term, noise has been associated with mortality due to respiratory causes (Tobias et al., 2014), and more specifically with pneumonia-, COPD- (chronic obstructive pulmonary disease) (Recio et al., 2016b) and diabetes-related mortality in the over-65 age group (Tobias et al., 2015b; Recio et al., 2016b), mortality due to cardiovascular causes (Tobías et al., 2015c) such as ischaemic heart disease, myocardial infarction and cerebrovascular disease (Recio et al., 2016b), hospital admissions due to organic and respiratory causes in the general (Tobias et al., 2001) and childhood population (Linares et al., 2006), and admissions due to circulatory causes (Tobias et al., 2001). Moreover, noise is a risk factor for adverse birth outcomes (Díaz and Linares, 2016), and can bring forward the time of birth by acting indirectly as a stress factor (Arroyo et al., 2016). On examining the influence of different environmental noise sources at children’s homes on incident mental health problems among school-aged children, a recent study (Dreger et al., 2015) found an association between nocturnal noise and the total difficulties score, emotional symptoms, and conduct problems. In the long term, noise has been associated with: total mortality; mortality due to cardiovascular causes (Halonen et al., 2015), myocardial infarction, and type II diabetes mellitus and hypertension (Barcelo et al., 2016); hospital admissions due to stroke (Halonen et al., 2015); development of diseases such as atherosclerosis (Kälsch et al., 2014); a higher risk of incident diabetes (Sørensen et al., 2013); and an increased risk of myocardial infarction among men (Babisch et al., 2005).

A meta-analysis of 14 studies (5 cohort, 4 case-control and 5 cross-sectional) published until 2013 (Babisch et al., 2014) showed that for weighted day-night noise levels lying in the range from 52 db(A) to 77 db(A), a rise of 10 db(A) increased the risk of coronary heart disease (CHD) by 8%. This association was also observed in Banerjee’s study (Banerjee et al., 2014) for noise levels of 65 db(A) upwards.

A narrative review conducted up to 2015 (Stansfeld et al., 2015) highlights: on the one hand, that with respect to air pollution, traffic noise has an independent effect on cardiovascular morbidity and mortality; and on the other, that in Europe, environmental noise ranks second in terms of disability adjusted life years lost (DALYs), ahead of other pollutants such as lead, ozone and dioxins. These independent health effects exerted by noise levels and air pollutants, even in cases where they share the same source, has also been observed in other studies undertaken in Madrid (Tobias et al., 2014, Tobias et al., 2015c), Barcelona (Barcelo et al., 2016) and London (Fecht et al., 2016), with moderate correlations in the last of the three.

Accordingly, the aim of this study was to ascertain the short-term effect of road-traffic noise levels on medical attention provided by the Madrid Regional Medical Emergency Service (Servicio de Urgencia Médica de Madrid/SUMMA 112) in response to public, telephone-based demand in the period from 01/01/2008 to 31/12/2009, with this being the first step towards establishing future associations in the very short term (hourly level).